This invention relates to synthetic detergents and in particular to improved methods for the manufacture of products made with synthetic detergents.
In the manufacture of products made with synthetic detergent compounds, in particular the manufacture of bars using synthetic detergents (xe2x80x9csyndet barsxe2x80x9d) and bars containing both synthetic detergents and soaps (xe2x80x9ccombinationxe2x80x9d or xe2x80x9ccombixe2x80x9d barsxe2x80x9d), it is known that the compounded detergent formulations are difficult to form into bars. Currently, such bars are made by processes similar to those used for making bars from natural soaps (based on the salts, usually alkali metal salts of naturally occurring fatty acids), in particular by compounding the basic ingredients into flakes or extruded xe2x80x9cnoodlesxe2x80x9d. Conventionally, these are made by mixing the raw materials using high shear blending of synthetic detergents, and in combi bars with soap(s), with a molten plasticiser in the presence of relatively small amounts of water. The result is a relatively inhomogeneous or macroscopic mixture. The mix is then flaked or extruded to give noodles. The bars are made from the flakes or noodles by working at moderately elevated temperatures using roll mixers and extruders (the processing in extruders is commonly referred to as xe2x80x9cploddingxe2x80x9d), followed by extrusion to form a slug of the compounded soap mixture which is then cut and pressed into the final bar form. A particular problem in the manufacture of syndet and combi bars is that the temperature range within which the plasticity of the formulation allows slug and bar manufacture is much narrower than is available in the manufacture of bars made from natural soaps. This necessitates relatively tight process control to make slugs and eventually bars which have adequate coherence to be of practical value. Even so, presently available syndet and combi bars are not fully satisfactory as products for domestic use. Further it is difficult to incorporate significant amounts of additives that provide useful properties in the final product as the additives typically cause changes in the plasticity profile of the overall mix sometimes causing softening and sometimes hardening, thus complicating processing.
This invention is based on the discovery that pre-processing a composition containing the synthetic detergent to produce a relatively finely divided powder or granulate can make subsequent processing much simpler, enabling the incorporation of additives more easily and at higher levels than is practical with conventional processing methods, and enabling the manufacture of products, particularly slugs to give cleansing bars which have superior uniformity and give better, particularly smoother, skin feel in use than conventional synthetic detergent cleansing bars.
Accordingly the present invention provides a method of making a formulated synthetic detergent product, which includes:
1 forming an aqueous dispersion or emulsion of a synthetic detergent and a hydrophobic plasticiser and optionally a filler; and
2 spray drying the dispersion or emulsion,
to produce a particulate product including the synthetic detergent and the hydrophobic plasticiser, and, optionally, the filler.
The invention includes a detergent material in particulate form which includes a synthetic detergent and a hydrophobic plasticiser and optionally a filler is a substantially homogeneous dispersion. In particular in this aspect of the invention, the detergent material is in particulate form including a synthetic detergent and an hydrophobic plasticiser, and, optionally, a filler, in substantially homogeneous dispersion, having a weight average particle size of from 150 to 1200 xcexcm, particularly in free flowing non-dusting particulate form.
The invention further includes a method of making bars of synthetic detergent materials which comprises forming a synthetic detergent material in particulate form of or made by the spray drying method of the invention into bars.
The invention additionally includes a personal care synthetic detergent cleansing bar product which has been made from a synthetic detergent material in particulate form of or made by the spray drying method of the invention.
The synthetic detergent is (typically) an anionic or non-ionic surfactant. Suitable anionic types of surfactant include alkyl sulphates, such as lauryl, myristyl, stearyl and cetyl sulphates, alkyl sulphonates, alkyl ether sulphates, alkyl glycerol ether sulphonates, alkyl phosphate esters, ethoxylated alkyl phosphate esters, sarcosinates, taurate derivatives, alkyl sulphoacetates, hydroxyalkyl sulphonate esters, such as isethionate esters, particularly of fatty carboxylic acids, for example cocoyl isethionic acid, lauryl isethionic acid and stearyl isethionic acid, usually used as an alkali metal e.g. sodium salt, alkyl sulphosuccinates, such as di-sodium and/or potassium lauryl, oleyl and stearyl sulphosuccinates, alkyl ether sulphosuccinates, alkyl sulphosuccinamates, and acyl glutamates. Such anionic surfactants are usually used as metal, usually alkali metal especially sodium or potassium, ammonium, ethanolamine or alkali earth metal particularly magnesium salts.
The alkyl chains in such surfactants are typically C9 to C20, more usually C14 to C18 chains. Suitable non-ionic types of surfactant include alkyl polysaccharides (more properly described as alkyl oligosaccharides) particularly where the saccharide residues are glucose residues and particularly where the alkyl groups are C8 to C16 alkyl groups, and especially lauryl or decyl glucoside, particularly having an average degree of polymerisation of from 1 to 2; sorbitan ester alkoxylates, particularly sorbitan laurate or stearate ethoxylates e.g. containing an average of from about 15 to about 30, particularly an average of about 20, ethylene oxide residues per molecule; glucamide surfactants such as glucamides of C8 to C22 acids; alcohol alkoxylate, particularly ethoxylate surfactants, especially C10 to C22 alkyl alkoxylates, particularly ethoxylates, typically containing 20 to 100 alkoxylate, particularly ethoxylate, residues; carboxylic acid ethoxylates especially of C10 to C22 carboxylic acids and containing 20 to 100 ethoxylate residues. The composition may also include ester surfactants such as glycerol mono-esters such as glyceryl mono-stearate, oleate or laurate, and citrate esters.
As is usual in personal care products, it is desirable to include mild surfactants. And it is for this reason that anionic surfactants where the hydrophile is the anionic residue of a relatively strong acid group, usually a sulphate or more usually a sulphonate group, are used in this invention. Typical examples of such surfactants include carboxylic acids including fatty, particularly C8 to C20 alkyl, esterified with hydroxyalkylsulphonic acids such as isethionic acid (2-hydroxyethane sulphonic acid; HO.CH2.CH2.SO3H), as salts, usually alkali metal salts, particularly sodium salts of C12 to C20 carboxylic isethionates, especially sodium cocoylisethionate and sulphosuccinate surfactants. Combinations of isethionate surfactants and sulphosuccinate surfactants, for example approximately equal proportions of sodium cocoyl isethionate and sodium sulphosuccinate, give particularly good results. Such mild surfactants can be used alone or in combination with other (more harsh) surfactants, but such mixtures will have intermediate mildness properties.
The use of such mild surfactants is an important feature of the invention such that it forms a specific part of the invention which accordingly includes a method of making a formulated synthetic detergent product, which comprises
1 forming an aqueous dispersion or emulsion of a surfactant composition comprising at least one fatty isethionate foaming surfactant, optionally but desirably at least one sulphosuccinate salt; a hydrophobic plasticiser; and optionally a filler; and
2 spray drying the dispersion or emulsion,
to produce a particulate product including the synthetic detergent and the hydrophobic plasticiser, and, optionally, the filler.
In such mild surfactant based products, the surfactant is desirably mainly or predominantly a mild surfactant, in particular, at least 50%, desirably at least 75% and especially at least 90%, by weight of the surfactant is a mild surfactant, particularly an alkyl sulphonate and/or a sulphosuccinate and/or a fatty isethionate. This forms a further specific aspect of the invention.
Other surfactants, particularly synthetic surfactants can be included in the synthetic detergent products of and made by the present invention. Suitable synthetic surfactants include amphoteric surfactants such as betaine derivatives, imidazoline derivatives, and fatty amphoacetates, particularly coco-amphoacetates. The composition may also include soaps, particularly fatty acid soaps, particularly alkali metal salt of fatty C12 to C20 carboxylic acids such as sodium and/or potassium stearate and/or myristate and/or cocoate. The amount of fatty acid soaps, when used, can vary widely. Relatively small amounts can be used to improve the cosmetic properties of syndet formulations such as foaming. In such applications the amount will usually be from 5 to 30% by weight based on the total amount of detergent in the composition. These levels are typical of some commercial combi-bar formulations. At such levels the soap may substitute for part of or add to the synthetic detergent in the formulation. Compositions containing relatively large amounts of soap can be considered as soap based compositions which include syndets to make them more mild or to make the base more compatible with additives. In such systems, the soap can be up to about 95%, typically 75 to 95%, by weight based on the total amount of detergent in the composition. Levels intermediate these ranges are used in combination formulations intended to have properties intermediate those of syndets and soaps. For such products the amount of soap is usually in the range 30 to 75%, more usually 40 to 60%, by weight based on the total amount of detergent in the composition.
When fatty acid soaps are included in the compositions, the manufacturing process for the bar products can involve including part or all of the soap in the emulsion which is spray dried, combining soap e.g. in the form of conventional noodles, flakes or pellets, with spray dried syndet powder or a combination of these.
The component described generally as a hydrophobic plasticiser serves the function of softening the detergent product to improve its workability, particularly in the manufacture of detergent bars. The manufacture of detergent bars is typically carried out at temperatures of from 35 to 50xc2x0 C. and the hydrophobic plasticisers used in the invention typically have melting or softening points from ambient temperature up to about 90xc2x0 C., desirably up to 50xc2x0 C. Suitable materials include fatty acids, particularly C12 to C22 fatty acids such as stearic, myristic and coconut oil fatty acids; fatty alcohols, particularly C14 to C22 fatty alcohols such as stearyl alcohol; waxes such as paraffin wax or hydrogenated oils such as hydrogenated castor oil and jojoba wax (hydrogenated jojoba oil).
The filler is an optional but very desirable component of the detergent formulation used in the invention. It is a relatively inert finely divided particulate material, usually having an average particle size of less than 50 xcexcm, typically from 2 to 25 xcexcm which provides binding, additional plasticity and improved skinfeel properties. The filler can be an organic material such as starch or an inorganic material such as talc.
The relative (percentage) proportions by weight of the detergent and the hydrophobic plasticiser are usually as follows:
When the filler is present the relative proportions of the detergent and the hydrophobic plasticiser are generally within the above ranges and the filler is added as from 2 to 25, particularly 8 to 22 and especially 10 to 20% of the three component system. This gives three component percentage compositions by weight typically as follows (including for clarity the no-filler proportions):
Other components such as are conventionally included in syndet and combi bars can be included for example polymers such as high molecular weight polyethylene glycol (PEG), typically having a molecular weight of greater than 100 kD and polysaccharides which improve binding, skinfeel and compatibility, conditioners such as polyquaternary ammonium compounds (polyquats) humectants such as glycerol and sorbitol ethoxylates such as sorbeth-30, emollient oils such as mineral oils e.g. isoparaffin oils, natural or synthetic triglycerides, propoxylates alkyl ethers, perfumes, pigments and dyes. Such materials will usually be included in conventional concentrations, for each type of these components typically from 0.1 to 5% by weight of the overall formulation. Depending on their nature, they can be included at any suitable stage in manufacture, by inclusion in the emulsion (for non-volatile components), by addition to the spray dried product or by inclusion at later stages of processing.
The dispersion or emulsion in water can be made up by simply dispersing the individual components, detergent(s), hydrophobic plasticiser and optionally filler in water and warming and stirring the mixture to form the dispersion or emulsion. However, it is generally desirably to preheat the water to about or above the melting temperature of the hydrophobic plasticiser, a typical range is from about 75 to about 90xc2x0 C., then to add the filler (if used) followed by the detergents and finally to add the hydrophobic plasticiser in liquid (molten) form and to stir the mixture. Generally high shear mixing is not needed to disperse or emulsify the components once the mixture has been made up. This makes the processing relatively simple and straightforward. The dispersion or emulsion is then spray dried typically by feeding the dispersion or emulsion to a spray drier using a heated stream of gas, typically air or nitrogen, usually as dry gas as the drying medium . The temperature of the dry gas will be high enough, and sufficiently above the dew point of the gas, to enable efficient removal of water i.e. to supply enough heat to evaporate the water present at the flow rates used, but not so high that it causes decomposition of the product. Typically, the dry gas temperature will be from 160 to 250xc2x0 C.
After spray drying the powdered detergent composition can be subject to mild agglomeration e.g. in a fluidized bed, particularly with the recirculation of fines, particularly to reduce the proportion of fines and modestly to increase the average particle size. This aggregation reduces dusting and eases the incorporation of additives. The weight average particle size of the spray dried detergent product is generally in the range from 50 to 1200 xcexcm. More usually, if the powder is not agglomerated, the weight average particle size is typically from 50 to 250 xcexcm and if it is agglomerated, the weight average particle size (after agglomeration) is typically from about 200 to about 750 xcexcm.
Bars can be made from the spray dried powder straightforwardly using conventional techniques (allowing for the form of the feedstock). Thus the powder can be charged to a mixer and appropriate amounts of water, perfume and other additives, if desired, such as oils, humectants e.g. glycerine, and plant extracts and be added and the composition mixed until the components are uniformly distributed. We have found that this can be more quickly than with detergents in the form of flakes or noodles. Thus, with the product produced according to the invention, mixing can be done in about 1 minute, where with flakes or noodles it would take 3 to 4 minutes. This can significantly enhance the output of the mixers without requiring investment in larger scale equipment. Further, because extended mixing increases the extent to which the compositions become soft and sticky, the ability to operate with short mixing times is an additional benefit.
The mixture is then passed to a bar making line where it can be milled in a 2 or 3-roll mill to give a sheet with the desired plasticity and temperature and then processed in a simplex extruder (usually fitted with a coarse grid) to extrude the slug of soap. In the conventional manufacture of syndet and combi bars, the milling step, particularly during start up, usually involves much adjustment of the set up to make a satisfactory product. We have found that using the spray dried product made by this invention, the set up of the milling stage is made much easier. Alternatively, the processing on the 2/3-roll mixer can be omitted and the mixture passed directly to a plodder e.g. a duplex (2-step) plodder, and the soap bare extruded. The route chosen will depend on the desired degree of homogeneity in the product. The extruded slug can then be cut and stamped to form the soap bar product.
Using the spray dried material of this invention, we have found that after mixing, as described above, the product can be passed directly to the plodder or extruder. This contrasts with manufacture using conventional flakes or noodles because these materials usually require processing in a simplex extruder or plodder and/or roll-mill to homogenise the product and to give it a suitable plasticity before further plodding and bar extrusion. We have further found that the time needed for a processing line to settle to steady state operating conditions is much shorter using the spray dried material according to this invention. We believe that this is because the spray dried material provides better filling of the volume of the extruder and improved surface contact and higher internal friction of the material being extruded leads to a much quicker equilibration of the temperature.
It is an advantage of this invention that the generally adverse effects on processability (in bar making) of mixer additives is much less than in conventional processes. Thus, much higher amounts of water can be included before the material becomes too soft to process. For example, using conventional flakes noodles or pellets, the maximum amount of water that can be added is typically from 2 to 4%, but using powder made according to the invention amounts as high as 10 to 13% can be added without major difficulty. Also, additives, such as perfumes, particularly alcohol or hydroalcohol based perfumes, that have an adverse effect on plasticity and binding in conventional systems sometimes making it impossible to extrude the detergent as a slug, have much reduced impact on the process carried out using the spray dried product according to this invention.
The invention includes a method of making a synthetic detergent bar which includes the steps of:
1 forming an aqueous dispersion or emulsion of a synthetic detergent and a hydrophobic plasticiser and optionally a filler; and
2 spray drying the dispersion or emulsion,
to produce a particulate product including the synthetic detergent and the hydrophobic plasticiser, and, optionally, the filler; and subsequently forming the particulate product including the synthetic detergent into a bar.
In particular the synthetic detergent bar can be made by mixing optional further components (if any) with the particulate product including the synthetic detergent followed by milling in a 2 or 3-roll mill of and subsequent processing in a simplex extruder (usually fitted with a coarse grid) to extrude the slug of soap which is subsequently cut and stamped into bars. Alternatively, the processing on the 2/3-roll mixer can be omitted and the mixture passed directly to a plodder e.g. a duplex (2-step) plodder, and the soap extruded as a slug which is subsequently cut and stamped into bars.